The DNR was unable to determine the cause of a fish kill in Whitewater Creek, Dubuque County, that occurred sometime in the first week of May.

"By the time we were notified and went out to investigate, the fish had been dead a few days and most of the pollutant had washed downstream," said Chris Gelner with the DNR's Manchester field office.

"I would encourage the public to call the DNR's 24-hour spill line at 515-725-8694 as soon as they see dead fish," he added. "It's not just the fish, it's important to identify the pollutant to protect people, livestock and wildlife downstream."

DNR found dead fish southeast of Epworth along more than six miles of the creek, from upstream of the Pilot Grove Road bridge to the North Cascade Road bridge. Investigators were able to rule out the Epworth and Peosta wastewater treatment plants as pollutant sources.

Field tests showed slightly elevated levels of ammonia in the stream.

The DNR will continue to investigate and monitor the situation.

The state of Iowa requires anyone responsible for the release of a hazardous material or manure to report it to the DNR as soon as possible but no later than six hours after the release began. See specific guidelines on the DNR's website.